[timdorr]

Why not both?

My Model S has these same controls embedded in the steering wheel. Volume, music control, and climate controls are all there.

That's actually where I find I spend most of my time interacting with the car. I usually only use the touchscreen for more complex things like manipulating the map. For complex inputs like choosing a song or entering my destination, I use the voice controls.

I don't think the solution is one interface. It's multiple interfaces that function best in certain contexts, with some overlap. Look at Google Glass for an example of this.